The fly fishing is a fishing method of casting a fly without weight and float from a remote position unable to be sensed by fishes, and drifting the fly on or in water. To meet such requirements, in the fly fishing, there has been used a five-part fishing equipment comprising a fly rod, a reel, a fly line, a leader and a fly.
Among these parts, as the leader, there have been preferably used those leaders which are reduced in thread diameter to realize natural drift thereof. The leader has been further required to have a tapered section through which an inertia force is smoothly transmitted from the fly line to the fly upon casting, thereby enabling the fly to be quietly dropped on a water surface. Consequently, the leader has been usually composed of a portion called "butt" and having a larger thread diameter, which is connected with the fly line, a portion called "taper" and having a tapered shape, and a portion called "tippet" and having a smaller thread diameter, at which the fly is fitted to the leader. Incidentally, in FIG. 1(a) showing an explanatory view of the above-mentioned leader, reference numeral (1) represents the leader, (2) represents the butt section (A), (3) represents the tapered section (B), and (4) represents the tippet section (C).
In addition, the leader is preferably comprising a material whose refractive index is close to that of water, so as to be unsensed by fishes. As such the materials having a refractive index close to that of water, there may be exemplified vinylidene fluoride-based resins. However, when the vinylidene fluoride-based resins are subjected to spinning process, it has been difficult to obtain a leader having a smooth shape. Especially, in the production of a tapered leader, a shape-unstable portion 6 (constriction) having a smaller diameter than an average diameter of the tipped section is formed at a connecting portion between the tapered section (B) and the tippet section (C), so that a stress due to tension caused upon fishing-up is concentrated on the constricted portion, thereby causing the leader to be cut thereat.
Further, in the case where the vinylidene fluoride-based resins are subjected to the spinning process, the obtained leader tends to suffer from melt fracture. Especially, the melt fracture is more remarkably caused upon the production of tapered leaders. That is, since the tapered leader is composed of the butt section (A), the tapered section (B) and the tippet section (C), it is required that the diameter of the leader is varied corresponding to the respective sections, so that the melt fracture is likely to occur. When a raw thread having such melt fracture is stretched to impart a mechanical strength thereto, the raw thread not only suffers from breakage but also is deteriorated in appearance of the surface thereof. Further, when vinylidene fluoride-based resins having an inherent viscosity less than the specific value is used to produce a leader, the obtained leader is deteriorated in natural drift property.
The present invention has been attained to overcome the above-mentioned problems. It is an object of the present invention to provide a leader for fly fishing which comprises a vinylidene fluoride-based resin, can show a high tensile strength or tenacity, is improved so as to inhibit a shape-unstable portion 6 (constriction) having a smaller diameter than an average diameter of the tippet section and melt fracture from being formed at a connecting portion between the tapered section (B) and the tippet section (C), and can exhibit an excellent natural drift property and a good appearance.